1. Field of the Invention
The present invention relates to a laminated heat exchanger, more particularly, which is constructed to close some of distribution channels in refrigerant distributing sections of tubes to uniformly distribute refrigerant into the tubes thereby improving flow distribution of refrigerant.
2. Background of the Related Art
A heat exchanger comprises internal flow channels so that refrigerant flows through the same while performing heat exchange with external air, and is applied to various air conditioning systems. Examples of the heat exchanger may include a fin tube type, a serpentine type, a drawn cup type and a parallel flow type which are used according to various conditions.
Hereinafter an evaporator of the heat exchangers using refrigerant as heat exchange medium will be described as an example.
As shown in FIGS. 1 to 6, the evaporator 1 comprises a pair of tanks 40a each having cups 14 with slots 14a formed at upper ends (or lower ends) thereof, a plurality of tubes 10 each having a refrigerant flow section 12 of a generally U-shaped configuration, which is formed by welding two plates 11 with a partitioning bead 13 extended to a predetermined length between a pair of tanks 40a and tanks 40 formed at both sides by the welded tanks 40a, heat radiator fins 50 laminated or stacked between the respective tubes 10 and two end plates 30 installed at outermost sides to reinforce the tubes 10 and the heat radiator fins 50.
In a pair of the plates 11 coupled to face each other, a number of beads 15 which are projected inward via embossment in order to impart turbulence to refrigerant flowing through the refrigerant flowing sections 12 of the tubes 10.
The opposing plates 11 on both sides are coupled to each other with a number of beads, 15 formed by embossing treatment, protruding inward, in order to make refrigerant flowing within the refrigerant flow sections 12 of the tubes 10 become turbulent.
Furthermore, refrigerant distribution sections 16 are provided at the inlet and outlet sides of the refrigerant flow sections 12 of the tubes 10, having a plurality of distribution channels 16b partitioned by a plurality of beads 16a for refrigerant uniform distribution into the refrigerant flow sections 12.
Meanwhile, two tank-type and four tank-type plates are identical except that an additional cup is provided at the bottom end. Therefore, only a plate 11 having a cup 14 formed at the upper end is given as an example, for clarity of explanation.
The tubes 10 are also provided with inlet side manifolds 17 protruding toward a side of the tanks 40 for communication with the inside and connected with inlet pipes 2 for refrigerant supply, as well as outlet side manifolds 17a connected with outlet pipes 3 for refrigerant discharge.
The manifolds 17, 17a are formed in the form of a circular pipe by coupling two plates having semicircular manifolds 17, 17a. The resulting manifolds 17, 17a are united with the inlet and outlet pipes 2, 3 by means of brazing material of a ring shape and brazed, thereby making it possible to couple the manifolds 17, 17a with the inlet and outlet pipes 2, 3.
Regarding refrigerant flow within the evaporator 1 configured as above, the tanks 40, having inlet side and outlet side manifolds 17, 17a formed for refrigerant, are provided with baffles 60 therein for partitioning between inflow refrigerant and discharged refrigerant.
Accordingly, the pair of tanks 40 are divided into inlet side 4 for inflow refrigerant and outlet side 5 for discharged refrigerant, from the standpoint of the baffles 60. Suppose that the tank 40 on the inlet side 4 is referred to as A, B and the tank 40 on the outlet side 5 is referred to as C, D in the drawings. Refrigerant supplied through the inlet side manifold 17 is then supplied to the A side of the tank 40, flows along the U-shaped refrigerant flow section 12 and finally directed into the B side of the adjacent tank 40 on the other side.
Refrigerant directed into the B side of the tank 40 flows to the C side of the same tank 40 and flows along the U-shaped refrigerant flow section 12 of the tubes 10. When refrigerant flows into the D side of the tank 40, it is finally discharged through the outlet side manifold 17a. 
In the process of causing inflow and discharge of refrigerant circulating in a cooling system through refrigerant lines, the evaporator 1 conducts evaporation through heat exchange with the air blown between the tubes 10. The endothermic action, due to the latent heat of evaporation of refrigerant, then cools the airblown to the inside of the vehicle room.
When refrigerant flows into the inlet side manifold 17, refrigerant is supposed to be distributed uniformly to both ends of the tank A side and flow to each of the tubes 10, as shown in FIG. 1. However, as the flow rate of refrigerant flowing directly into the refrigerant flow section 12 of the tube 10a having the manifold 17 formed increases, uniform distribution to both ends of the A side of the tank 40 is not guaranteed. This causes irregular distribution of refrigerant flowing in the tubes 10.
According to the type of installation of the evaporator 1 in the air-conditioning device of a vehicle, a top tank-type, wherein the tank 40 faces upward, and a bottom tank-type, wherein the tank 40 faces downwards, are utilized, as shown in FIG. 5. In case of the top tank-type, refrigerant is mainly subject to gravity when it flows in through the manifold 17 and is subject to an inertial force when it makes a U-turn through the refrigerant flow section 12, thereby flowing along the outer shell of the refrigerant flow section 12 of the tube 10a having manifolds formed.
In case of the bottom tank-type, refrigerant is subject to an inertial force when it flows in through the manifold 17 and is mainly subject to a gravity when it makes a U-turn through the refrigerant flow section 12, thereby flowing near the partitioning bead 13.
Such uneven flow of refrigerant causes poor flow distribution of refrigerant in the refrigerant flow section 12 of the tube 10a having the manifold 17 formed and uneven heat exchange with the air passing between the tubes 10, 10a. This leads to considerable fluctuation in the temperature distribution of the discharged air. Consequently, the performance of the air-conditioning system becomes unstable.
Furthermore, more refrigerant flows to the tube 10 adjoining the tube 10a having the manifold 17 formed while lesser refrigerant flows nearer to both ends. This causes a supercooled area and an over-heated area. Even an icing problem occurs on the surface of the evaporator 1 in the supercooled area.
An approach to solve the above-mentioned problem is described, as an embodiment, in a registered Korea patent No. 352,876 issued to the assignee of the invention, entitled “Plate for Heat Exchanger Having Enhanced Evaporating Performance and Heat Exchanger Using It”, the whole contents thereof are incorporated herein for reference. It will now be explained briefly with reference to FIG. 6.
The refrigerant distribution section, 16 formed at the inlet and outlet sides of the refrigerant flow section 12 of the tube 10a having the manifold 17, is provided with a plurality of distribution channels 16b partitioned by a plurality of beads 16a, as shown in the drawing.
The inlet side refrigerant distribution section 16 of the refrigerant flow section 12 adjoining the manifold 17 is formed in such a manner that two outermost distribution channels are interrupted.
Accordingly, cooling effect is increased by improving the flow distribution of refrigerant, which is a problem of the prior art, to a degree.
When refrigerant flows into the inlet side manifold 17, the flow rate of refrigerant flowing directly to the refrigerant flow section 12 through the refrigerant distribution section 16 of the tube 10a is small. As a result, refrigerant is distributed uniformly to both ends of tank A side shown in FIG. 1 and flows toward each of the tank 10.
At the same time, any uneven flow of refrigerant into the refrigerant flow section 12 is prevented, during inflow of refrigerant into the manifold 17.
Although any uneven flow of refrigerant into the refrigerant flow section 12 can be prevented by interrupting the two outermost distribution channels at the inlet side refrigerant distribution section 16 of the refrigerant flow section 12, the approach still has a problem in that the outlet side refrigerant distribution section 16 of the refrigerant flow section 12 has the same structure as in the prior art, that is, has no interrupted distribution channels. As a result, refrigerant still flows uneven and the effect of flow distribution of refrigerant is unreliable.
Meanwhile, from the standpoint of the baffle 60, refrigerant undergoes heat exchange while passing through the inlet side tubes 4 and then flows toward the outlet side 5. In other words, refrigerant flows from tank 40 B side of the inlet side 4 to the tank 40 C side of the outlet side 5.
When the refrigerant flows from the B side of the tank 40 to the C side of the same tank 40, it is supposed to be distributed uniformly and flow into the tubes 10, 10a positioned at the C side. However, the refrigerant flowing from the B side tank 40 to the C side tank 40 is mainly subject to a gravity. Accordingly, as the refrigerant approaches the end of the C side tank 40, the amount of refrigerant flowing into each of the tubes 10, 10a decreases. This results in the problem that the refrigerant is not distributed uniformly to each of the tubes 10, 10a. 
Therefore, considerable fluctuation occurs in the surface temperature at the outlet surface of the evaporator 1 and this becomes worse when less refrigerant flows or less air passes through the evaporator 1.
Furthermore, a supercooled area is formed in the tube 10 having more refrigerant flow and an over-heated area is formed in the tube having lesser refrigerant flow. This causes poor heat exchange with the air passing between the tubes 10. As a result, considerable fluctuation occurs in the temperature distribution of the discharged air.
Even an icing problem occurs on the surface of the evaporator 1 in the supercooled area, thereby making the air-conditioning system unstable. In the over-heated area, cooling and dehumidification of discharged air is not conducted properly. This result in the problem in that humid air of elevated temperature is introduced into the vehicle room and irritates the passengers.